How do you spot a fake Facebook user? People have many strategies, including looking at the content on their Wall, checking their mutual friends, and/or just scanning for anything out of the ordinary. Security firm Barracuda Networks has taken it a step further in a study titled "Facebook: Fake Profiles vs. Real Users."

The study analyzed a random sampling of 2,884 active Facebook accounts to identify key differences between average real user accounts and fake accounts created by attackers and spammers. You can see the results in the infographic above, or if you prefer, a quick summary follows:

Almost 60 percent of fake accounts claim to be bisexual, 10 times more than real users

Fake accounts have six times more friends than real users, 726 versus 130

Fake accounts use photo tags over 100 times more than real users, 136 tags per four photos versus one tag per four photos

Fake accounts almost always (97 percent) claim to be female, as opposed to 40 percent for real users

"Likes, News Feeds and Apps have helped lead Facebook to its social network dominance and now attackers are harnessing those same features to efficiently scale their efforts," Dr. Paul Judge, chief research officer at Barracuda Networks, said in a statement. "These fake profiles and apps give attackers a long-lived path to continuously present malicious links to innocent users. Also, researchers have shown how friending malicious accounts can lead to account takeover using Facebook’s trusted friend account recovery. We have analyzed thousands of fake accounts to determine features and patterns that distinguish them from real users, and created a feature-based heuristic engine to distinguish real users from fake profiles."

Millions of Facebook users tend to accept friend requests blindly. That's why social bots can be so effective. Next time you get a friend request, ask yourself: "Do I really know this person?"